1. Technical Field
The present invention relates to a transmission method for multiplexing modulation signals of a plurality of channels to the same frequency band, a transmission apparatus and a reception apparatus.
2. Description of the Related Art
This kind of transmission method and reception method have been available such as the ones disclosed in Japanese Patent Application Non-Examined Publication No. 2002-44051. FIG. 87 illustrates the transmission method and the reception method disclosed in the foregoing publication.
In FIG. 87, first space-time encoder STE1 (8705) receives first data block b1 [n, k], and second space-time encoder STE2 (8707) receives second data block b2 [n, k], and two signals coded by encoders STE1 and STE2 respectively are modulated by inverse fast Fourier transformers IFFT (8708-8711). Then the modulated signals are transmitted as OFDM (orthogonal frequency division multiplexing) signals by four transmitting antennas TA1 (8712)-TA4 (8715).
A plurality of receiving antennas RA1 (8701)-RAP (8703) receive those signals transmitted by antennas TA1 (8712)-TA4 (8715). Reception signals rl [n, k] (8716)-rp (8718) are transformed by fast Fourier transformation (FET) sub-systems FFT1 (8719)-FFTp (8721) respectively, and supplied to space-time processor STP (8722). Processor STP (8722) detects signal information and supplies it to first and second space-time decoders STD1 (8723) and STD2 (8724). Channel parameter estimation unit CPE (8725) receives the transformed signal, and determines channel-parameter information, then supplies the information to the space-time processor STP (8722) for demodulating the signals.
However, the foregoing conventional structure gives no thought to the synchronization between channels in the same frequency band as well as a frequency offset. As a result, this structure encounters the difficulty of achieving the most important factor in order to demultiplex a multiplexed signal, namely, obtaining an accuracy of estimating channels.